Kinetics of Copper(I)-Catalyzed Dimerization and Hydration of Acetylene in Water

Abstract

Abstract The kinetics of the dimerization and hydration of acetylene in water with a copper(I) catalyst, a so-called Nieuwland catalyst, were investigated. The stationary state kinetics for both reactions could be described assuming that the rate-controlling step is a second-order reaction of an activated catalyst, [H···Cl–Cu–C2H], formed in the reaction mixture, with acetylene or water. The activation energies and activation entropies were 12.4 kcal·mol−1 and −33.3 cal·mol−1·K−1 for the acetylene dimerization, and 17.5 kcal·mol−1 and −34.2 cal·mol−1·K−1 for the acetylene hydration, respectively. The large negative values of activation entropy for these reactions may be accounted for by the role of water as a kind of cocatalyst.